Automatic Lamp

Automatic lamp

This circuit will turn on an AC Bulb when the sun sets, the working of the circuit is simple and the heart of this circuit is an LDR(Light Dependent Resistor) that is wired as a light sensor thus when the ambient light falls on the LDR the circuit will not work and when the ambient light fails to fall on the (when the sun sets) LDR the circuit will turn on a 230V ac bulb or CFL

circuit diagram of automatic lamp

how it works?

A TRIAC is used here instead of a relay, a triac can switch high voltage AC. The voltage to trigger the triac gets from the emitter of T1 so since resistance of the LDR is low as it is in day light the T1 will not get sufficient positive voltage to trigger the triac but in darkness the resistance of LDR is very low this causes to turn the T1 on so the triac will get triggered and the bulb will glow. D1 and R1 are used to rectify AC and lower the voltage, C1,R1 used to pass 6 VDC for T1. the R3 can be set to a desired level to turn the light on as the level of sunlight.

Pinout of triac

this circuit is not isolated from mains! Touching any parts of the circuit while connected to mains may cause to pass high voltage through your body and may kill you! If you are a newbie in electronics then don’t build this circuit!


About Ztronn

hellooo i'm lsid ,i am a DIY (do it yourself) stuff loving kinda guy, i mean i love to build things and posting it on my blogs for the world to see. i love reading about technology and innovation. i love the nature,mysteries of space and of course God. no aliens. kindly let me know what you think about my simple innovations in the comments.
This entry was posted in high voltage, useful and tagged , , . Bookmark the permalink.

17 Responses to Automatic Lamp

  1. WICKEY says:

    hi what is the Z1 5V

  2. Arif ALEEM Shamsi says:

    Great and very simple diagram, thanks
    Arif (

  3. jamshid says:

    instead of sto can we use any other triac?

  4. vishnu says:

    how get pcb layout?

  5. antony says:

    is the pin out of triac to 220 and st 044 are same????

  6. parandhaman.g says:

    onces on the circuit ,we have to touch the ldr know

  7. Dileepa says:

    What is the Triac Number …. I would like to know whether i can use this circuit for LED bulbs (230V) ?

  8. athar says:

    what is the value of C1….?

  9. razz says:

    T1 is directly connected to TRIAC / T1 connecting the wire C1 and Z1….you pls clarify me.

Leave a reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s